1. Field of the Invention
This invention relates to an image reading apparatus for color images, more particularly to a image reading apparatus using one-dimensional color sensors whose one picture element is comprised by three different sensor elements for sensing three primary colors; red, green and blue which respectively are successfully aligned as one image element in series.
2. Description of the Prior Art
CCD (Charged Coupled Device) one-dimensional image sensors, which are aligned in series in order to sense, for example, the three primary colors; red, green and blue are well known as a color sensor to be used in reading apparatus for color images. Such color sensors contain respective red (R), green (G) and blue (B) filters which are aligned adjacently each picture element by vapor deposition and other techniques, so that fundamentally the data are outputted serially in the order of R.fwdarw.G.fwdarw.B, while the data comprising a set of R, G and B are converted through a color conversion processing into respective data for the three primary colors for printing.
In such a conventional color conversion method, however, the density of image reading is equal to the picture element density of the sensor, in other words, the density of image reading can not be increased over the picture element density, for example 16 per 1 mm in general.
In the prior art therefore, the read image data are processed electrically in order to generate the picture elements and consequently improve the picture element density, resulting in problems such as a need for complicated software processings and longer processing time.